Many adhesives and cementitious compositions such as construction mortars, concretes and plasters are typically formulated with a water-retention aid to improve the characteristics thereof. By employing a water-retention aid, water loss is prevented and the rheological properties are improved. Typically, water-retention aids are used in ceramic tile adhesive compositions to prevent water absorption by the ceramic tile or substrate to which the tile is applied.
To be functional in the construction industry, a ceramic tile composition must be easily spreadable and in conjunction the composition must support the tile during the period in which the composition sets. Typically, a thin-bed mortar composition used to set ceramic tile with a preference for thin bed motors contains: sand, cement, and cellulose ethers. It is known that cellulose ethers extend the working time of the thin-bed composition, acting as a water-retention aid.
Unfortunately, cellulose ethers do not contribute to sag resistance, or resistance to movement of the tile that is applied to the thin-bed mortar composition in a vertical surface. However, as disclosed in Bermudez. U.S. Pat. No. 4,487,864, when cellulose ethers are crosslinked to form a modified water-soluble carbohydrate, the carbohydrate is useful as a water-retention aid and as an adhesive.
Another method of controlling sagging is disclosed in Bernett, U.S. Pat. No. 4,021,257. Bernett discloses the use of long chain organic polymers which function as flocculants, aiding in sag resistance. In practice, typically, the most operable compositions are mixtures of clays with cellulose ethers and polyacrylamide flocculants, but these are costly and have handling disadvantages.
Thus, it would be highly desirable to have a composition which has all three properties - good rheology, good bond characteristics, has water-retention properties, and can be used efficiently without cost and handling disadvantages.